Communication networks may be broadly classified under two distinct categories: circuit-switching networks and packet-switching networks. The public switched telephone network (PSTN) is an example of a circuit-switching network, while the Internet is an example of a packet-switching network. Other examples of packet-switching networks include a PC local area network (LAN) and a corporate wide-area network (WAN).
Packet-switching networks employ a multitude of protocols, including transport protocols such as Transport Control Protocol/Internet Protocol (TCP/IP) and Ethernet; as well as language protocols such as Hypertext markup language (HTML) and Extensible markup language (XML). While the power of a packet-switching network, such as the Internet, lies in its adaptability to heterogeneous applications using a variety of formats and protocols to transport data packets, this heterogeneous approach proves to be a challenge in terms of characterizing the transport qualities of the various subnets that constitute the overall network. A part of this challenge arises from errors that are generated in the process of translating formats related to a data packet that originates from one end of a packet-switching network and is transported over multiple network links before arriving at its destination.
As an example of such a process, a PC may originate an Ethernet-formatted data packet that is transported over a LAN to a webserver, wherein the webserver extracts the data packet and reformats it as an IP packet that is transported over a TCP link. This TCP link may incorporate an intermediate link that uses an Asynchronous Transfer Mode (ATM) format. When this occurs, the TCP/IP data packet has to be translated into the ATM format, which may subsequently be carried over a fiber-optic link requiring the ATM cells to be further translated into a format such as synchronous optical network (SONET). At the receiving end, the SONET, ATM, and TCP/IP formats have to be suitably converted to a format that the receiving device, such as a PC, can utilize to extract the originally transmitted data packet. This process of format-translations typically leads to errors in the received data packet due to transmission defects in devices, and faults in the transmission links of one or more intermediate networks.
Troubleshooting an end-to-end packet-switching network path to identify such a faulty intermediate network is a daunting task involving format-translations and measurements of various parameters. This task is further exacerbated by the sheer volume of data packets being carried over the intermediate networks in the packet-switching network. Processing such a large volume of digital data, to identify a transmission fault, especially one that occurs infrequently, typically turns out to be an imprecise exercise.
The power of large packet-switching networks such as the Internet also lies in its capacity to provide alternative transmission paths when a failure occurs in a transmission link that is currently in use. This failure may occur, for example, due to a hardware failure in a router, or due to traffic congestion from an excessive flow of data bits through a packet switching node. Unlike a fixed end-to-end transmission link the performance of which may be characterized with a certain degree of reliability, the introduction of alternative switching paths makes the task of such network characterization even harder. For example, if a particular switched path has a measurable bit-error-rate (BER) over a certain period of time, the BER may change for the same switched path during a subsequent interval of time. If an alternative switched path is now introduced, the BER of the alternative switched path may be different from that of the previously used one, and also subject to change over time with no clear correlation of the new BER values to the BER values measured earlier upon the previous path.
Therefore, while characterization of a fixed end-to-end transmission link is in itself a difficult task, this characterization becomes more complicated and unreliable when alternative switching paths are introduced. A network analyzer using a fixed threshold for measuring the BER performance of such a packet-switching network may prove inadequate in characterizing the packet-switching network when using such a measuring technique. As such, it is desirable to provide network characterization solutions that can adapt to changing network parameters and measure transmission parameters that can be used to accurately define network conditions.